let's start with what are you using to make your game?
Git only needs to contain your code and game assets - sprites, textures, models, sound and so on. runing into maximum size issue this early usually means you are adding too much to the repo.
For example, Unity project folder can take around 2 or 3 GB even for samll game but all git really needs is assets folder that can be under 100MB. and I belieave Unreal Engine does this too.
Github even provides option tocreate repo with default .gitignore file template for most popular engines